As air travel has increased over the past decades, airport facilities have become more crowded and congested. Minimizing the time between the arrival of an aircraft and its departure to maintain an airline's flight schedule, and also to make a gate or parking location available without delay to an incoming aircraft, has become an airline priority. The safe and efficient ground movement of a large number of aircraft simultaneously into and out of the ramp and gates areas has become increasingly important. As airline fuel costs and safety concerns and regulations have increased, use of the aircraft main engines is no longer the best option for achieving the desired safe and efficient ground movement.
Various alternatives to the use of an aircraft's main engines to move an aircraft on the ground have been tried. The use of a tug or tow vehicle to move an aircraft into and out of a gate or parking location can eliminate the need to use the aircraft main engines. This option, however, is not without its own challenges and costs. More ground vehicles requiring more fuel and more ground personnel to operate them, add to an already congested environment in the gate area. Restricted use of the aircraft engines on low power during arrival at or departure from a gate is an additional option. This option is also problematic. Not only does engine use consume fuel, it is also noisy, and the associated safety hazards of jet blast and engine ingestion in a congested area are significant concerns that cannot be overlooked.
The use of a motor structure integrally mounted with a wheel to rotate the wheel and drive a vehicle, including an aircraft, has been proposed. The use of such a structure, ideally, could move an aircraft with minimal or no use of an aircraft's main engines. In U.S. Pat. No. 2,430,163, for example, Dever describes a motor that may be incorporated in an aircraft landing gear wheel in which the stator is mounted on a stationary part of a wheel assembly and the rotor is connected to the revolving part of the wheel to produce a high rotating torque near the periphery of the wheel. The structure described by Dever, while likely to have been suitable for World War II era aircraft, is not likely to be as effective in the gear wheels of contemporary aircraft. Other patent art, such as U.S. Pat. No. 3,977,631 to Jenny, also describe drive motors associated with aircraft gear wheels intended to drive an aircraft on the ground. The motor assembly disclosed by Jenny is selectively coupled to an aircraft wheel through a rotatably mounted brake apparatus in which the normally non-rotating stator is rotatably mounted and driven. In U.S. Pat. No. 7,445,178, McCoskey et al describe a powered nose aircraft wheel system with a multifunctional wheel motor coupled to the wheel axle and the wheel. A dual cone clutch structure is required to be actuated to allow the wheel motor to spin the wheel freely prior to landing and to change the direction of wheel rotation from forward to reverse. U.S. Pat. No. 7,226,018 to Sullivan also describes a wheel motor useful in an aircraft landing gear wheel. This wheel hub motor/generator disks stack includes within the stack alternating rotor and stator disks and is designed to provide motive force to an aircraft wheel when electric power is applied. The arrangement is stated to function as a unique aircraft braking system that also converts kinetic energy into electrical energy. None of the foregoing patents suggests a compact motor assembly capable of powering an aircraft drive wheel that could be easily installed in the limited landing gear space available on an existing aircraft without substantial modification. This art, moreover, does not contemplate an integral configuration of the motor components that sheds heat during operation and that provides easy access to the motor components for maintenance and repair when the motor is not in operation.
Published U.S. patent applications, including U.S. Patent Application Publication Nos. US2006/0273686 to Edelson, US2007/0282491 to Cox et al, US2009/0152055 to Cox, US2009/0261197 to Cox, International Patent Application Publication No. WO 2008/027458 to Cox et al, and British Patent No. 2457144, owned in common with the present invention, describe aircraft drive systems that use electric drive motors to power aircraft wheels and move an aircraft on the ground. These disclosures focus on specific aspects of the drive systems and motor assemblies, including drive system data, motor design, tire profile, and motor cooling, rather than on integrally configuring motor components with landing gear wheel components to maximize the available space without changes to the aircraft landing gear.
A need exists, therefore, for an electric motor assembly for an aircraft gear wheel designed to fit integrally within the aircraft wheel and efficiently with other existing components into the limited space available for the aircraft landing gear without changes to the existing components.